A known material which is both impermeable to water and which is soluble or dispersible in water is one which comprises a combination of polyvinyl alcohol and a gelation accelerator for polyvinyl alcohol. Specifically, such a material is composed of a polyvinyl alcohol film having formed thereon an absorption and retention layer constituted by a powder of a highly water-absorptive polymer and a powder of a gelation accelerator for polyvinyl alcohol. A sanitary napkin utilizing this material has been proposed (JP-B-59-13213, corresponding to U.S. Pat. No. 4,333,464). (The term "JP-B" as used herein means an "examined Japanese patent publication".) This sanitary napkin is considered to function as follows. The gelation accelerator for polyvinyl alcohol dissolves in the water contained in menstrual blood absorbed by the absorption and retention layer, and the resulting aqueous solution of the gelation accelerator wets the polyvinyl alcohol film to form a temporary insoluble gel. Thus, the sanitary napkin can exhibit a leakage preventing effect. When this napkin is immersed in a large quantity of water of water, the concentration of the gelation accelerator is lowered and, as a result, the gel collapses and becomes water-soluble or water-dispersible.
In the above-described sanitary napkin, the concentration in menstrual blood of the gelation accelerator for polyvinyl alcohol is an important point in order for the polyvinyl alcohol film to undergo gelation with the aid of the gelation accelerator. Although the range of gelation accelerator concentrations that can cause gelation varies depending on the kind of the gelation accelerator, it has been difficult with such a system to always and completely prevent the leakage of menstrual blood.
In JP-A-63-181758 (the term "JP-A" as used herein means an "unexamined published Japanese patent application") (corresponding to U.S. Pat. Nos. 4,762,738, 4,830,187 & 4,930,942), an ostomy pouch is proposed which can be thrown away by means of flushing in an ordinary toilet. This ostomy pouch is produced by joining a front panel consisting of a water-swellable and cold water-insoluble film material having a water-resistant layer laminated thereto to a rear panel consisting of a water-swellable and cold water-insoluble film material having a layer laminated thereto. Since this ostomy pouch employs water-swellable and cold water-insoluble film materials on the inner side thereof, it becomes viscous upon contact with water in a toilet stool to thereby pass through the drainage piping system.
However, such an ostomy pouch employing a water-swellable and cold water-insoluble film material has the problem that since its inner-side film layer is water-swellable, complete water resistance cannot be obtained when feces, etc., having a high water content are to be held therein, although it is possible to hold substances with a low water content.